I can't figure out how they got the answers they did on these questions.

Can anyone out there help?

For 81 I get (c) for an anwer not (d) Maybe something to do with
it being a parallel circuit instead of a series. Didn't know they had
different
formulas.

I get (c) for 86. Same story.

I get 300 - j318 for (88)

Can't figure out the other two also.




81] What is the impedance of a network composed of a
100-picofarad capacitor in parallel with a 4000-ohm resistor, at
500 kHz? (Specify your answer in polar coordinates.)

a} 2490 ohms, /51.5 degrees.

b} 4000 ohms, /38.5 degrees.

c} 5112 ohms, / -38.5 degrees.

d} 2490 ohms, /-51.5 degrees.@@




86] What is the impedance of a network composed of a
400-ohm-reactance inductor in parallel with a 300-ohm resistor?
(Specify your answer in polar coordinates.)

a} 240 ohms, / 36.9 degrees.@@

b} 240 ohms, / -36.9 degrees.

c} 500 ohms, / 53.1 degrees.

d} 500 ohms, / -53.1 degrees.



88] What is the impedance of a network composed of a
0.01-microfarad capacitor in parallel with a 300-ohm resistor, at
50 kHz? (Specify your answer in rectangular coordinates.)

a} 150 - j159.

b} 150 + j159.

c} 159 + j150.

d} 159 - j150.@@







111] A 6 volt battery with 1.2 ohms internal resistance is
connected across two 3 watt bulbs. What is the current flow?

a} .57 amps.

b} .83 amps.@@

c} 1.0 amps.

d} 6.0 amps.



129] How many capacitors of 400 volts and 2.0 microfarads each
would be necessary to obtain a combination rated at 1600 volts
and 1.5 microfarads?

a} 10.

b} 12.@@

c} 14.

d} 16.

Two different formulas and methods for series and parallel AC Circuits;

See URL:
http://www.tpub.com/neets/book2/4l.htm

For 81 in brief calculate Xc
Xc = 3,183 ohms
R=4000 ohms

Assume 4,000 volts
E/R = 1 amp
E/Xc = 1.257 amps

Iz = square root of Ir squared + Ix squared = 1.606 amps

Z=e/Iz = 4000/1.606 = 2490 ohms

For phase angle --- You can use Power Factor = true power divided by
apparent power = 4000/6424 = 0.6225 = PF
and PF is the cos of the phase angle
So cos 0.6225 is = 51.5 degrees
Did some rouning off here and there

Gurus -- check my math.
--
73 From The Signal In The Noise
Caveat Lector Ya All

============================================
"carter" wrote in message
...
I can't figure out how they got the answers they did on these questions.

Can anyone out there help?

For 81 I get (c) for an anwer not (d) Maybe something to do with
it being a parallel circuit instead of a series. Didn't know they had
different
formulas.

I get (c) for 86. Same story.

I get 300 - j318 for (88)

Can't figure out the other two also.




81] What is the impedance of a network composed of a
100-picofarad capacitor in parallel with a 4000-ohm resistor, at
500 kHz? (Specify your answer in polar coordinates.)

a} 2490 ohms, /51.5 degrees.

b} 4000 ohms, /38.5 degrees.

c} 5112 ohms, / -38.5 degrees.

d} 2490 ohms, /-51.5 degrees.@@




86] What is the impedance of a network composed of a
400-ohm-reactance inductor in parallel with a 300-ohm resistor?
(Specify your answer in polar coordinates.)

a} 240 ohms, / 36.9 degrees.@@

b} 240 ohms, / -36.9 degrees.

c} 500 ohms, / 53.1 degrees.

d} 500 ohms, / -53.1 degrees.



88] What is the impedance of a network composed of a
0.01-microfarad capacitor in parallel with a 300-ohm resistor, at
50 kHz? (Specify your answer in rectangular coordinates.)

a} 150 - j159.

b} 150 + j159.

c} 159 + j150.

d} 159 - j150.@@







111] A 6 volt battery with 1.2 ohms internal resistance is
connected across two 3 watt bulbs. What is the current flow?

a} .57 amps.

b} .83 amps.@@

c} 1.0 amps.

d} 6.0 amps.



129] How many capacitors of 400 volts and 2.0 microfarads each
would be necessary to obtain a combination rated at 1600 volts
and 1.5 microfarads?

a} 10.

b} 12.@@

c} 14.

d} 16.